1. Field of the Invention
The present invention relates to a bar code reader, more particularly, to a bar code reader capable of properly preventing a bar code from being read double.
2. Description of the Related Art
In recent years, it has been generalized that commercial goods are managed by bar codes as typified by a POS system in the sector of distribution industries etc. For example, in the POS system in a shop, pieces of information on classifications and sales prices etc of the goods are coded in a format of the bar code and printed on the goods. The bar code is read at the check-out counter, and a payment is made based on the read information. Then, the number of sold goods is counted in real time, and a result of count serves an inventory management and a stocking management.
Incidentally, the bar code reader is roughly classified into a fixed type bar code reader integrally incorporated into a register device, and a handy type bar code reader operable while being held by a hand and connected via a communication cable to the register device.
On the other hand, the bar code is printed on a label stuck to a commercial goods or a container of the commercial goods in a case where it is difficult to print the bar code on the commercial goods itself (e.g., perishable foods) (i.e., in-store marking), and is printed on a bar code list BL as shown in FIG. 14 in a case where it is difficult to stick the label thereto (e.g., fast-food and foods sold by weights). This bar code list BL is a sheet on which goods names GN of a multiplicity of goods and corresponding bar codes BC are printed, and prepared in the vicinity of the register device (e.g., on the upper surface of the register device). Then, a casher at the register, when selling the goods with the bar code list BL on which the goods name GN is written, reads the bar code BC corresponding to the goods name GN from this bar code list BL by use of the handy type bar code reader.
The conventional handy type bar code reader, especially, the bar code reader of such a type as to manipulate a laser beam, is not designed in consideration of reading the bar code printed on the above bar code list BL. Accordingly, in the case of reading the bar code printed on the bar code list BL by using the conventional handy type bar code reader, it is impossible to obviate a problem of double-reading which will hereinafter be explained.
To be specific, the conventional handy type bar code reader has hitherto been also mounted with a double-reading preventive mechanism for preventing the double-reading when reading the bar code stuck to the external surface of normal goods. This double-reading preventive mechanism includes a buffer for storing only one piece of demodulated data corresponding to the whole bar code, and a double-reading preventive timer for measuring an elapse time since the demodulated data has been once obtained. Then, this double-reading preventive mechanism, upon obtaining the demodulated data once by reading the bar code, writes this piece of demodulated data to the buffer and starts the double-reading preventive timer. Subsequently, this double-reading preventive mechanism, when the same demodulated data is obtained once again till the double-reading preventive timer makes a time-up after a predetermined time has elapsed, conceives that the same bar code is read twice, and invalidates the demodulated data obtained second time onwards.
On the other hand, when the bar codes BC written on the bar code list BL are read sequentially from above by use of the handy type bar code reader, it might happen that a scan beam accidentally scans the bar code read last time and the bar code read previous time before last on the occasion of raising the handy type bar code reader away from the bar code list BC. In such a case, the double-reading preventive mechanism incorporated into the conventional handy type bar code reader prevents the double-reading of only the bar code read last time (i.e., the buffer is stored with only the demodulated data corresponding to the bar code read last time), and consequently the demodulated data obtained by scanning the bar code once again by accident, which has been read previous time before last or read more previously than that time, might be treated as being valid.